The report says many young people may face a jobless future
One in five teenagers receiving their GCSE results next week could be receiving unemployment benefit by the time they are 21, a report says.
Those leaving with no qualifications are twice as likely to sign on as those with qualifications, the report adds.
The Prince's Trust and Sheffield University base their predictions on trends seen during previous recessions.
Their study suggests current 18 to 25 year olds could be the hardest hit in that age group since the 1929 crash.
Figures released on Wednesday showed 2,435,000 people were out of work.
The government said it was investing billions of pounds to give youngsters training and work opportunities.
The Prince's Trust report was compiled by professor of human geography at Sheffield University, Danny Dorling, who said that if the current recession played out like those of the 1970s, 80s and 90s, the UK could see mass levels of youth unemployment.
"If the number of young people on the dole exceeds a million, this summer's school leavers will be the hardest hit since the 1929 crash - with those without qualifications worst off," he said.
He said a million young people out of work would be particularly alarming, given that it is now very hard to claim unemployment benefit at the age of 18 and a third of young people now go on to university.
The number of young people in England not in employment or training has risen to 935,000, according to government figures released last week.
Paul Brown from the Prince's Trust and school leaver Chelsea Stewart on why young people could be hit by the recession
Professor Dorling said the government needed to do more to tackle the problem of high youth unemployment.
"It could instruct universities to take more students this year and next, it could speed up the apprenticeship programme and it could fund, at very modest cost, conservation projects for example.
"The rate of youth unemployment in the recession to come will depend almost entirely on what opportunities young people are offered. This is why we must act now."
The danger of not acting now was greater health problems in young people, higher levels of violent crime and weaker social infrastructures in affected neighbourhoods, he added.
Martina Milburn, chief executive of the Prince's Trust, said: "If a million young people sign on for just two weeks, the cost to the state will be more than £100m.
"It is more important than ever that we support those with fewest qualifications before they become a lost generation."
A government spokesman said: "We agree with the Prince's Trust that we have to help young people.
"That's why in July we launched Backing Young Britain, a cross-government campaign which aims to bring businesses and public and voluntary sectors together to ensure that the valuable skills and experience of our young people aren't being wasted.
"The government is already... investing more than £6.9bn to deliver more than 1.5 million learning opportunities for 16 to 18 year olds, and more than £1bn to deliver an additional 200,000 employment opportunities and 100,000 apprenticeships for 19 to 24-year-olds.
"Our Graduate Talent Pool helps create and match people to internships and assists more graduates in kick-starting their careers by gaining the skills and experience they need to get-on through an internship and will offer a great way for companies to inject fresh talent into the workplace."
The Prince's Trust says its research suggests health and social care and some areas of hospitality are likely to remain stable and even experience growth in the recession.
The trust is setting up new training opportunities in these sectors in an attempt to develop young people's skills.
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